I. Field of the Invention
This invention pertains to brake mechanisms for slowing or stopping movement of a rotary disc. More particularly, this invention pertains to such brake mechanisms with means for assuring positive retraction of the braking mechanism from the rotary disc when the brake is disengaged.
II. Description of the Prior Art
Disc brakes are widely used on automobiles, trucks, motor homes and other vehicles. Conventional disc brakes comprise a pair of friction pads disposed on opposite sides of a rotatable disc. When a brake is engaged, the friction pads are displaced towards the disc to clamp the disc between the friction pads. Commonly, the friction pads are forced towards the disc by means of hydraulic pressure. In such applications, a piston is provided within a cylinder with opposing surfaces of the piston and the cylinder defining a pressure chamber. Pressurized hydraulic fluid within the pressure chamber urges the piston toward a brake friction pad causing the friction pad to move towards the brake rotor. As the piston urges the friction pad towards the rotor, a resilient piston seal is deformed. When the brake is disengaged, the hydraulic pressure is relieved and the deformation of the piston seal provides a force to urge the piston back to its original position with the friction pad moving away from the rotor.
Frequently, the deformation of the piston seal does not provide a sufficient force to return the friction pads to their disengaged position. This is particularly true in vehicles that are not driven regularly. As a result, the friction pads rub on the rotor causing numerous problems such as brake fade; excess wear on the pads, tires and disc; early wheel bearing failure; reduced fuel mileage; front end shimmy and steering instability.
In the prior art, disc brakes having apparatus for retracting brake pads when the brake is disengaged are known. An example of such is found in U.S. Pat. No. 4,364,455 to Oshima dated Dec. 21, 1982. Oshima teaches a disc brake having friction pads disposed on both sides of a rotatable disc. The friction pads are supported by a stationary member. A resilient member such as a coil spring, is provided between the stationary member and the friction pad for biasing the friction pad in a direction separating the pad from the disc. U.S. Pat. No. 3,008,546 to Erickson dated Nov. 14, 1961 shows a disc brake adjuster having springs mounted on headed nails with one end of the nails connected to a brake pad backing. The springs are compressed as the brake pad moves toward the brake disc. When the brake is disengaged, the force of compression in the springs urges the brake pad away from the disc. The spring and headed nails are mounted in a threaded spring mechanism which may be adjusted to vary a gap between the brake pad and brake disc without varying the compression of the spring.
While the prior art teaches disc brakes having spring actuated mechanisms for urging brake pads away from a brake rotor when the brake is disengaged, such apparatus incorporate designs which are dedicated for the particular brake mechanism in which they are employed. That is, such designs are not readily adaptable to existing brake structure so as to permit retroactive modification of brakes not incorporating such apparatus by design. Also, it would be desirable to have brakes with automatic retraction apparatus whereby the force of the retraction mechanism and the gap between the brake pads and the brake rotor may be readily and independently adjusted.